xref: /titanic_41/usr/src/cmd/ssh/sshd/auth-krb4.c (revision 7c478bd95313f5f23a4c958a745db2134aa03244)
1 /*
2  * Copyright (c) 1999 Dug Song.  All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  *
13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23  */
24 
25 #include "includes.h"
26 RCSID("$OpenBSD: auth-krb4.c,v 1.28 2002/09/26 11:38:43 markus Exp $");
27 
28 #pragma ident	"%Z%%M%	%I%	%E% SMI"
29 
30 #include "ssh.h"
31 #include "ssh1.h"
32 #include "packet.h"
33 #include "xmalloc.h"
34 #include "log.h"
35 #include "servconf.h"
36 #include "uidswap.h"
37 #include "auth.h"
38 
39 #ifdef AFS
40 #include "radix.h"
41 #endif
42 
43 #ifdef KRB4
44 extern ServerOptions options;
45 
46 static int
krb4_init(void * context)47 krb4_init(void *context)
48 {
49 	static int cleanup_registered = 0;
50 	Authctxt *authctxt = (Authctxt *)context;
51 	const char *tkt_root = TKT_ROOT;
52 	struct stat st;
53 	int fd;
54 
55 	if (!authctxt->krb4_ticket_file) {
56 		/* Set unique ticket string manually since we're still root. */
57 		authctxt->krb4_ticket_file = xmalloc(MAXPATHLEN);
58 #ifdef AFS
59 		if (lstat("/ticket", &st) != -1)
60 			tkt_root = "/ticket/";
61 #endif /* AFS */
62 		snprintf(authctxt->krb4_ticket_file, MAXPATHLEN, "%s%u_%ld",
63 		    tkt_root, authctxt->pw->pw_uid, (long)getpid());
64 		krb_set_tkt_string(authctxt->krb4_ticket_file);
65 	}
66 	/* Register ticket cleanup in case of fatal error. */
67 	if (!cleanup_registered) {
68 		fatal_add_cleanup(krb4_cleanup_proc, authctxt);
69 		cleanup_registered = 1;
70 	}
71 	/* Try to create our ticket file. */
72 	if ((fd = mkstemp(authctxt->krb4_ticket_file)) != -1) {
73 		close(fd);
74 		return (1);
75 	}
76 	/* Ticket file exists - make sure user owns it (just passed ticket). */
77 	if (lstat(authctxt->krb4_ticket_file, &st) != -1) {
78 		if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
79 		    st.st_uid == authctxt->pw->pw_uid)
80 			return (1);
81 	}
82 	/* Failure - cancel cleanup function, leaving ticket for inspection. */
83 	log("WARNING: bad ticket file %s", authctxt->krb4_ticket_file);
84 
85 	fatal_remove_cleanup(krb4_cleanup_proc, authctxt);
86 	cleanup_registered = 0;
87 
88 	xfree(authctxt->krb4_ticket_file);
89 	authctxt->krb4_ticket_file = NULL;
90 
91 	return (0);
92 }
93 
94 /*
95  * try krb4 authentication,
96  * return 1 on success, 0 on failure, -1 if krb4 is not available
97  */
98 int
auth_krb4_password(Authctxt * authctxt,const char * password)99 auth_krb4_password(Authctxt *authctxt, const char *password)
100 {
101 	AUTH_DAT adata;
102 	KTEXT_ST tkt;
103 	struct hostent *hp;
104 	struct passwd *pw;
105 	char localhost[MAXHOSTNAMELEN], phost[INST_SZ], realm[REALM_SZ];
106 	u_int32_t faddr;
107 	int r;
108 
109 	if ((pw = authctxt->pw) == NULL)
110 		return (0);
111 
112 	/*
113 	 * Try Kerberos password authentication only for non-root
114 	 * users and only if Kerberos is installed.
115 	 */
116 	if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
117 		/* Set up our ticket file. */
118 		if (!krb4_init(authctxt)) {
119 			log("Couldn't initialize Kerberos ticket file for %s!",
120 			    pw->pw_name);
121 			goto failure;
122 		}
123 		/* Try to get TGT using our password. */
124 		r = krb_get_pw_in_tkt((char *) pw->pw_name, "", realm,
125 		    "krbtgt", realm, DEFAULT_TKT_LIFE, (char *)password);
126 		if (r != INTK_OK) {
127 			debug("Kerberos v4 password authentication for %s "
128 			    "failed: %s", pw->pw_name, krb_err_txt[r]);
129 			goto failure;
130 		}
131 		/* Successful authentication. */
132 		chown(tkt_string(), pw->pw_uid, pw->pw_gid);
133 
134 		/*
135 		 * Now that we have a TGT, try to get a local
136 		 * "rcmd" ticket to ensure that we are not talking
137 		 * to a bogus Kerberos server.
138 		 */
139 		gethostname(localhost, sizeof(localhost));
140 		strlcpy(phost, (char *)krb_get_phost(localhost),
141 		    sizeof(phost));
142 		r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
143 
144 		if (r == KSUCCESS) {
145 			if ((hp = gethostbyname(localhost)) == NULL) {
146 				log("Couldn't get local host address!");
147 				goto failure;
148 			}
149 			memmove((void *)&faddr, (void *)hp->h_addr,
150 			    sizeof(faddr));
151 
152 			/* Verify our "rcmd" ticket. */
153 			r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
154 			    faddr, &adata, "");
155 			if (r == RD_AP_UNDEC) {
156 				/*
157 				 * Probably didn't have a srvtab on
158 				 * localhost. Disallow login.
159 				 */
160 				log("Kerberos v4 TGT for %s unverifiable, "
161 				    "no srvtab installed? krb_rd_req: %s",
162 				    pw->pw_name, krb_err_txt[r]);
163 				goto failure;
164 			} else if (r != KSUCCESS) {
165 				log("Kerberos v4 %s ticket unverifiable: %s",
166 				    KRB4_SERVICE_NAME, krb_err_txt[r]);
167 				goto failure;
168 			}
169 		} else if (r == KDC_PR_UNKNOWN) {
170 			/*
171 			 * Disallow login if no rcmd service exists, and
172 			 * log the error.
173 			 */
174 			log("Kerberos v4 TGT for %s unverifiable: %s; %s.%s "
175 			    "not registered, or srvtab is wrong?", pw->pw_name,
176 			    krb_err_txt[r], KRB4_SERVICE_NAME, phost);
177 			goto failure;
178 		} else {
179 			/*
180 			 * TGT is bad, forget it. Possibly spoofed!
181 			 */
182 			debug("WARNING: Kerberos v4 TGT possibly spoofed "
183 			    "for %s: %s", pw->pw_name, krb_err_txt[r]);
184 			goto failure;
185 		}
186 		/* Authentication succeeded. */
187 		return (1);
188 	} else
189 		/* Logging in as root or no local Kerberos realm. */
190 		debug("Unable to authenticate to Kerberos.");
191 
192  failure:
193 	krb4_cleanup_proc(authctxt);
194 
195 	if (!options.kerberos_or_local_passwd)
196 		return (0);
197 
198 	/* Fall back to ordinary passwd authentication. */
199 	return (-1);
200 }
201 
202 void
krb4_cleanup_proc(void * context)203 krb4_cleanup_proc(void *context)
204 {
205 	Authctxt *authctxt = (Authctxt *)context;
206 	debug("krb4_cleanup_proc called");
207 	if (authctxt->krb4_ticket_file) {
208 		(void) dest_tkt();
209 		xfree(authctxt->krb4_ticket_file);
210 		authctxt->krb4_ticket_file = NULL;
211 	}
212 }
213 
214 int
auth_krb4(Authctxt * authctxt,KTEXT auth,char ** client,KTEXT reply)215 auth_krb4(Authctxt *authctxt, KTEXT auth, char **client, KTEXT reply)
216 {
217 	AUTH_DAT adat = {0};
218 	Key_schedule schedule;
219 	struct sockaddr_in local, foreign;
220 	char instance[INST_SZ];
221 	socklen_t slen;
222 	u_int cksum;
223 	int r, s;
224 
225 	s = packet_get_connection_in();
226 
227 	slen = sizeof(local);
228 	memset(&local, 0, sizeof(local));
229 	if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
230 		debug("getsockname failed: %.100s", strerror(errno));
231 	slen = sizeof(foreign);
232 	memset(&foreign, 0, sizeof(foreign));
233 	if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
234 		debug("getpeername failed: %.100s", strerror(errno));
235 		fatal_cleanup();
236 	}
237 	instance[0] = '*';
238 	instance[1] = 0;
239 
240 	/* Get the encrypted request, challenge, and session key. */
241 	if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance,
242 	    0, &adat, ""))) {
243 		debug("Kerberos v4 krb_rd_req: %.100s", krb_err_txt[r]);
244 		return (0);
245 	}
246 	des_key_sched((des_cblock *) adat.session, schedule);
247 
248 	*client = xmalloc(MAX_K_NAME_SZ);
249 	(void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
250 	    *adat.pinst ? "." : "", adat.pinst, adat.prealm);
251 
252 	/* Check ~/.klogin authorization now. */
253 	if (kuserok(&adat, authctxt->user) != KSUCCESS) {
254 		log("Kerberos v4 .klogin authorization failed for %s to "
255 		    "account %s", *client, authctxt->user);
256 		xfree(*client);
257 		*client = NULL;
258 		return (0);
259 	}
260 	/* Increment the checksum, and return it encrypted with the
261 	   session key. */
262 	cksum = adat.checksum + 1;
263 	cksum = htonl(cksum);
264 
265 	/* If we can't successfully encrypt the checksum, we send back an
266 	   empty message, admitting our failure. */
267 	if ((r = krb_mk_priv((u_char *) & cksum, reply->dat, sizeof(cksum) + 1,
268 	    schedule, &adat.session, &local, &foreign)) < 0) {
269 		debug("Kerberos v4 mk_priv: (%d) %s", r, krb_err_txt[r]);
270 		reply->dat[0] = 0;
271 		reply->length = 0;
272 	} else
273 		reply->length = r;
274 
275 	/* Clear session key. */
276 	memset(&adat.session, 0, sizeof(&adat.session));
277 	return (1);
278 }
279 #endif /* KRB4 */
280 
281 #ifdef AFS
282 int
auth_krb4_tgt(Authctxt * authctxt,const char * string)283 auth_krb4_tgt(Authctxt *authctxt, const char *string)
284 {
285 	CREDENTIALS creds;
286 	struct passwd *pw;
287 
288 	if ((pw = authctxt->pw) == NULL)
289 		goto failure;
290 
291 	temporarily_use_uid(pw);
292 
293 	if (!radix_to_creds(string, &creds)) {
294 		log("Protocol error decoding Kerberos v4 TGT");
295 		goto failure;
296 	}
297 	if (strncmp(creds.service, "", 1) == 0)	/* backward compatibility */
298 		strlcpy(creds.service, "krbtgt", sizeof creds.service);
299 
300 	if (strcmp(creds.service, "krbtgt")) {
301 		log("Kerberos v4 TGT (%s%s%s@%s) rejected for %s",
302 		    creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
303 		    creds.realm, pw->pw_name);
304 		goto failure;
305 	}
306 	if (!krb4_init(authctxt))
307 		goto failure;
308 
309 	if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
310 		goto failure;
311 
312 	if (save_credentials(creds.service, creds.instance, creds.realm,
313 	    creds.session, creds.lifetime, creds.kvno, &creds.ticket_st,
314 	    creds.issue_date) != KSUCCESS) {
315 		debug("Kerberos v4 TGT refused: couldn't save credentials");
316 		goto failure;
317 	}
318 	/* Successful authentication, passed all checks. */
319 	chown(tkt_string(), pw->pw_uid, pw->pw_gid);
320 
321 	debug("Kerberos v4 TGT accepted (%s%s%s@%s)",
322 	    creds.pname, creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
323 	memset(&creds, 0, sizeof(creds));
324 
325 	restore_uid();
326 
327 	return (1);
328 
329  failure:
330 	krb4_cleanup_proc(authctxt);
331 	memset(&creds, 0, sizeof(creds));
332 	restore_uid();
333 
334 	return (0);
335 }
336 
337 int
auth_afs_token(Authctxt * authctxt,const char * token_string)338 auth_afs_token(Authctxt *authctxt, const char *token_string)
339 {
340 	CREDENTIALS creds;
341 	struct passwd *pw;
342 	uid_t uid;
343 
344 	if ((pw = authctxt->pw) == NULL)
345 		return (0);
346 
347 	if (!radix_to_creds(token_string, &creds)) {
348 		log("Protocol error decoding AFS token");
349 		return (0);
350 	}
351 	if (strncmp(creds.service, "", 1) == 0)	/* backward compatibility */
352 		strlcpy(creds.service, "afs", sizeof creds.service);
353 
354 	if (strncmp(creds.pname, "AFS ID ", 7) == 0)
355 		uid = atoi(creds.pname + 7);
356 	else
357 		uid = pw->pw_uid;
358 
359 	if (kafs_settoken(creds.realm, uid, &creds)) {
360 		log("AFS token (%s@%s) rejected for %s",
361 		    creds.pname, creds.realm, pw->pw_name);
362 		memset(&creds, 0, sizeof(creds));
363 		return (0);
364 	}
365 	debug("AFS token accepted (%s@%s)", creds.pname, creds.realm);
366 	memset(&creds, 0, sizeof(creds));
367 
368 	return (1);
369 }
370 #endif /* AFS */
371